be on the telephone
​1 to be using the phone
He's on the telephone at the moment.
You're wanted (= somebody wants to speak to you) on the telephone.
TOPICS Phones, email and the internet A2
​2 (British English, old-fashioned) to have a phone in your home or place of work
We were not on the telephone at the cottage.
This expression became old-fashioned when mobile phones came into use. These days we would say: ‘We don't have a landline at the cottage.’
TOPICS Phones, email and the internet C2